1961—2018年青海高原极端气温指数时空变化特征

Spatiotemporal Variations of Extreme Temperature Indices over Qinghai Plateau During 1961-2018

基于1961—2018年青海高原49个地面气象观测站点的逐日最高和最低气温资料,选取8个极端气温指数,采用线性倾向估计、突变检验、尺度分离以及相关分析等方法,分析青海高原极端气温指数的时空变化特征。结果表明:(1)近58 a来,青海高原极端气温暖指数呈显著增加趋势,极端气温冷指数呈显著减少趋势,夜指数变化速率大于昼指数;(2)暖昼日数、冷昼日数、暖持续日数、最高温极低值、最低温极高值在1996年前后发生突变;(3)各指数表现出准3 a、5~6 a、10~15 a、24~31 a以及更长时间尺度的周期振荡,其中以准3 a周期变化最显著,暖持续日数和最高温极低值的准3 a周期振荡对原序列的贡献率在50%以上;(4)极端气温暖指数的增加以及冷指数的减少速率在柴达木盆地和东部农业区最快;(5)大部分极端气温指数倾向率的绝对值自低纬向高纬、由高海拔向低海拔地区递增。

Based on the daily maximum and minimum temperature data from 49 observation stations over Qinghai plateau during 1961-2018,the eight extreme temperature indices were slected by using methods of linear regression,Mann-Kendall test,time scales separation and correlation analysis,and the spatiotemporal variations of extreme temperature indices over Qinghai plateau were analyzed.The results are as follows:(1)The extreme temperature warm indices had significant rising trends,while the extreme temperature cold indices decreased significantly.The indices in nights became warming faster than indices in daytime.(2)The abrupt change points for the warm days(TX90P),cold days(TX10P),warm spell duration(WSDI),the minimum value of daily maximum temperature(TXN)and the maximum value of daily minimum temperature(TNX)occurred before and after 1996.(3)There were 3 a,5-6 a,10-15 a,24-31 a or longer quasi-cycle oscillations for extreme temperature indices during 1961-2018.Among them,the 3-year quasi-cycle oscillation was most significant,especially for WSDI and TXN that the amplitude of 3-year time-scale oscillation occupied a dominant position and the contribution rate to raw time series was above 50%.(4)The extreme warm(cold)indices increased(decreased)at the fastest rate in the Qaidam Basin and the eastern agricultural region.(5)The absolute values for most extreme temperature indices trends accelerated from high to low elevations and from low to high latitudes.